Valve trim and straight stroke valve

Abstract

The invention provides a valve internal part and a straight stroke valve, and belongs to the technical field of valves, the valve internal part comprises a sealing ring, a valve core and a welding corrugated pipe; a valve rod penetrates through the sealing ring; the valve element is arranged at the end of the valve rod, an extending part extending towards the fluid channel is arranged on the valve element, and the extending part is always in sliding fit with the inner wall of the fluid channel in the process that the fluid channel is opened and closed through the valve element. The welding corrugated pipe is arranged on the outer side of the valve rod in a sleeving mode, the first end of the welding corrugated pipe is welded to the sealing ring, the second end of the welding corrugated pipe is welded to the valve element, a balance hole communicating an inner cavity of the welding corrugated pipe with the fluid channel is formed in the valve element, and the balance hole is opened and closed so that the valve can be converted into a balanced type and an unbalanced type. Guiding is conducted through limiting cooperation of the extending part and the sealing ring at the two ends, a balance cylinder and a sleeve are omitted, the number of parts is reduced, the structure is simpler, and installation is convenient. According to the valve internal part, the problems that in the prior art, a balance type valve body is large in number of internal parts and complex in structure are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of valves, and in particular to a valve trim and a linear travel valve. Background Art

[0002] Industrial processes with fluids (such as petroleum, chemical, oil refining, electricity, pipelines, pulp and paper, etc.) generally require the use of stop valves or control valves, especially linear control valves, which have good performance in full process control. When the linear control valve is working, the pressure difference before and after the valve acts on the valve core, which will generate thrust on the valve core. The thrust of the unbalanced valve is completely applied to the valve core, and the balanced valve adopts certain measures to reduce or eliminate the thrust. The balanced valve has lower requirements on the actuator output and control system than the unbalanced valve, but the sealing level is lower than the unbalanced valve of the same model.

[0003] The sliding seal (Packing) of linear control valves has always been the focus of quality issues in terms of leakage level. Bellows is the best solution to completely solve the sliding seal of unbalanced linear valves, ensuring the highest level of zero external leakage. However, the traditional external bellows structure requires the design of additional complex accessories such as pressure-bearing sleeves, which increases the volume of the pressure-bearing part of the valve, increases the number of leakage points and increases the cost dramatically.

[0004] Chinese patent document (CN212564475U) discloses a bellows balanced sleeve valve, in which a valve plug is arranged in the valve body, and the valve plug is driven by a valve stem to open or close the valve. A balancing hole is arranged on the valve plug to maintain the pressure balance on the upper and lower sides of the valve plug when the valve is closed.

[0005] In the above scheme, a balancing cylinder and a bellows are further provided in the valve body, the balancing cylinder is sealingly arranged between the upper valve cover and the valve body, one end of the bellows is welded to the balancing cylinder, and the other end is welded to the valve plug. In the above scheme, the structure of the balancing cylinder includes a cylindrical structure extending toward the bellows, and the outer corrugation of the bellows is attached to the inner wall of the balancing cylinder by the arrangement of the cylindrical structure of the balancing cylinder, so as to guide and limit the bellows, so that the telescopic movement of the bellows is more stable.

[0006] In the above scheme, a sleeve is also provided in the valve body, and the sleeve is installed on the valve body for secondary guiding, so that the valve plug is easy to center during use and is not prone to tilting, misalignment, etc.

[0007] However, in the above solution, the cylindrical structure of the balance cylinder and the arrangement of the sleeve in the valve body result in a large number of parts in the valve body, a complex structure, and inconvenience in production and assembly. Summary of the invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the problem of the large number of internal parts and complex structure of the balanced valve body in the prior art, thereby providing a valve trim and a straight-stroke valve; at the same time, this simple built-in bellows valve trim structure can block the balancing hole, thus turning it into an unbalanced straight-stroke valve.

[0009] In order to solve the above technical problems, the present invention provides a valve internal component, which is used to be arranged in a valve body, including: a sealing ring, a valve core and a welded bellows; a valve stem is passed through the sealing ring; the valve core is arranged at the end of the valve stem, and the valve core is used to close the fluid channel in the valve body, and the valve core has an extension portion extending toward the fluid channel. During the process of the valve core opening and closing the fluid channel, the extension portion always slides with the inner wall of the fluid channel; the welded bellows is sleeved on the outer side of the valve stem, the first end of the welded bellows is welded to the sealing ring, and the second end of the welded bellows is welded to the valve core, and a balancing hole is provided on the valve core, and the balancing hole passes through the valve core to connect the inner cavity of the welded bellows with the fluid channel.

[0010] When in use, the valve trim is applied to the valve body. In the process of the valve core opening and closing the fluid channel, the valve stem is limited by the sealing ring, and the extension slides along the inner wall of the fluid channel. The limiting cooperation at both ends of the valve trim plays a guiding role for the valve core and the valve stem, omitting the balancing cylinder and the sleeve, reducing the number of parts, making the structure simpler and convenient for installation; the welded bellows has a good compression ratio, saves space compared to the traditional molded bellows, can be designed to be built into the valve body, and the self-centering effect of the welded bellows under pressure can assist in guiding and shock absorbing the valve core and the valve stem; the fluid medium enters the inner cavity of the welded bellows through the balancing hole on the valve core, the unbalanced forces are relatively offset, and a dynamic balance is formed in the valve body to ensure the smooth operation of the valve. The welded bellows can also play a sealing role to prevent internal leakage; the valve trim provided by the present invention solves the problem of more internal parts and complex structure of the balanced valve body in the prior art, and at the same time improves the closing level of the balanced straight-through valve.

[0011] Optionally, the valve core has a guide portion extending toward the fluid channel, the guide portion has a plurality of guide portions arranged at circumferential intervals around the valve core, and the extension portion is arranged at the extension end of the guide portion. Through the above arrangement, in the process of the valve core opening and closing the fluid channel, the guide portion drives the extension portion to slide in the valve seat, playing a role in guiding the movement trajectory of the valve core. When the valve core is opened to the maximum position, the extension portion on the guide portion maintains a blocking cooperation with the valve seat, which can reduce the shaking of the valve core and the valve stem under the impact of the fluid medium, and prevent the valve core from being offset relative to the valve seat, resulting in failure to normally close the fluid channel.

[0012] Optionally, the guide portion and the extension portion have an arc-shaped outer wall. Through the above arrangement, the arc-shaped outer wall can make the guide portion and the extension portion fit with the inner wall of the opening of the valve seat, thereby enhancing the sliding stability of the guide portion and the limit portion in the valve seat.

[0013] Optionally, both sides of the guide part are arc-shaped, so that a flow guide port is formed between the two guide parts. Through the above arrangement, when the valve core opens the fluid channel, the fluid medium flows in the valve body through the flow guide port between the two guide parts, and the two sides of the arc on the guide part can guide the fluid medium when it flows through the flow guide port, thereby reducing disturbance.

[0014] Optionally, the width of the guide port gradually increases in a direction away from the valve core. Through the above arrangement, in the process of the valve core opening and closing the fluid channel, the guide portion slides along the valve seat, and as the distance between the valve core and the valve seat changes, the area of ​​the guide port exposed to the valve seat changes linearly, so that the flow area between the valve core and the valve seat changes, thereby being able to adjust the flow rate.

[0015] Optionally, there is a gap between the roots of two adjacent guide parts. Through the above arrangement, a guide port with a certain flow area can be provided between the roots of two adjacent guide parts to prevent the flow area between the valve core and the valve seat from being too small when the valve core is opened slightly.

[0016] Optionally, the two side edges of the extension portion are in a straight line shape. Through the above arrangement, the two straight side edges can make the extension portion evenly stressed.

[0017] Optionally, a sliding seal is provided between the sealing ring and the valve stem. Through the above arrangement, it is possible to prevent the fluid medium in the inner cavity of the welding bellows from leaking outwards.

[0018] Optionally, a sealing member for blocking is provided in the balancing hole. Through the above arrangement, the sealing member can block the balancing hole, and can block and seal the balancing hole, so that the balanced valve trim can be converted into an unbalanced valve trim, and the welded bellows can prevent external leakage, so that the same structure can be turned into a zero-leakage unbalanced valve with a built-in welded bellows, achieving zero external leakage, and can increase the applicable range of valve trims and valve types.

[0019] The present invention provides a straight-stroke valve, comprising: a valve body, a valve seat, a valve cover and a valve trim as described in any one of the above schemes, wherein the valve body has a fluid passage, the valve seat is arranged in the fluid passage, the valve trim is arranged in the valve body, the valve trim is in sealing contact with the valve seat, and the valve cover is arranged on the upper end surface of the valve body. Due to the use of the above valve trim, a dynamic balance is formed in the valve body to ensure the smooth operation of the valve, thus having any of the above advantages.

[0020] Optionally, a flange is provided on the circumference of the valve core, a first groove is provided on the valve seat, a static seal is provided in the first groove, and in a closed state, the flange is embedded in the first groove; a second groove is provided on the valve body, a sealing ring of the valve trim is embedded in the second groove, a static seal is provided in the second groove, and the static seal is located between the sealing ring of the valve trim and the valve body; a sealing cavity is provided on the top of the valve cover, a part of the valve stem extending out of the valve cover is located in the sealing cavity, a driving mechanism is provided above the sealing cavity, a driving rod of the driving mechanism extends into the sealing cavity and is connected with the valve stem. Through the above arrangement, during the operation of the valve, the valve cover will generate a dynamic clamping force, and the sealing ring can disperse and evenly transmit the pressure to ensure that the entire circumferential surface is evenly stressed, thereby protecting the static seal in the second groove from unnecessary damage, keeping the static seal from deformation after being stressed, and avoiding leakage; when the valve core is closed, the flange is embedded in the first groove and squeezes the static seal to ensure the sealing between the valve core and the valve seat; the sealing chamber can protect the valve stem extending out of the valve cover, and drive the valve stem to rotate through the driving mechanism, thereby driving the valve operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of an implementation of a valve trim provided in an embodiment of the present invention;

[0023] Figure 2 It is a left side schematic diagram of the valve trim;

[0024] Figure 3 for Figure 1 Schematic diagram of a plugging seal provided in the middle balancing hole.

[0025] Description of reference numerals:

[0026] 1. Sealing ring; 2. Valve stem; 3. Valve core; 4. Welded bellows; 5. Balance hole; 6. Guide part; 7. Diversion port; 8. Curved surface structure; 9. Extension part; 10. Valve body; 11. Valve seat; 12. Valve cover; 13. First groove; 14. Second groove; 15. Sealing chamber; 16. Driving mechanism; 17. Sealing element. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] This embodiment provides a balanced valve trim structure for opening and closing the valve.

[0032] like Figure 1 As shown, a specific implementation of a valve trim provided in the present embodiment is used to be arranged in a valve body 10, comprising: a sealing ring 1, a valve core 3 and a welded bellows 4; a valve stem 2 is passed through the sealing ring 1; the valve core 3 is arranged at the end of the valve stem 2, the valve core 3 is used to close the fluid channel in the valve body 10, the valve core 3 has an extension portion 9 extending toward the fluid channel, and in the process of the valve core 3 opening and closing the fluid channel, the extension portion 9 always slides with the inner wall of the fluid channel; the welded bellows 4 is sleeved on the outer side of the valve stem 2, the first end of the welded bellows 4 is welded to the sealing ring 1, the second end of the welded bellows 4 is welded to the valve core 3, and a balancing hole 5 is arranged on the valve core 3, and the balancing hole 5 passes through the valve core 3 to connect the inner cavity of the welded bellows 4 with the fluid channel.

[0033] When in use, the valve trim is applied to the valve body 10. During the process of the valve core 3 opening and closing the fluid channel, the valve stem 2 is limited by the sealing ring 1, and the extension portion 9 slides along the inner wall of the fluid channel. The limiting cooperation at both ends of the valve trim guides the valve core 3 and the valve stem 2, omitting the balancing cylinder and sleeve, reducing the number of parts, making the structure simpler and convenient for installation; the welded bellows 4 has a good compression ratio, saves space compared to the traditional molded bellows, and can be implemented in the The valve body 10 is designed to be built-in, and the self-centering effect of the welded bellows 4 under pressure can assist the guidance and shock absorption of the valve core 3 and the valve stem 2; the fluid medium enters the inner cavity of the welded bellows 4 through the balancing hole 5 on the valve core 3, and the unbalanced forces are relatively offset to form a dynamic balance in the valve body 10 to ensure the smooth operation of the valve. The welded bellows 4 can also play a sealing role to prevent internal leakage; the valve internals provided in this embodiment solve the problem of the large number of internal parts and complex structure of the balanced valve body 10 in the prior art.

[0034] It should be noted that the valve trim provided in this embodiment can transform an unbalanced valve trim into a balanced valve trim by providing a balancing hole 5 on the valve core 3. According to the valve size and application conditions, one or more balancing holes 5 can be provided.

[0035] like Figure 1 , Figure 2 As shown, in the valve trim provided in this embodiment, the valve core 3 has a guide portion 6 extending toward the fluid channel, and the guide portion 6 has a plurality of guide portions 6 arranged at circumferential intervals around the valve core 3, and the extension portion 9 is arranged at the extension end of the guide portion 6. In the process of the valve core 3 opening and closing the fluid channel, the guide portion 6 drives the extension portion 9 to slide in the valve seat 11, and plays a role in guiding the movement trajectory of the valve core 3. When the valve core 3 is opened to the maximum position, the extension portion 9 on the guide portion 6 maintains a blocking cooperation with the valve seat 11, and under the impact of the fluid medium, the shaking of the valve core 3 and the valve stem 2 can be reduced, and the valve core 3 is prevented from being offset relative to the valve seat 11, resulting in failure to normally close the fluid channel. In addition, as an alternative embodiment, the guide portion 6 can also be omitted, and the extension portion 9 extending toward the fluid channel is provided on the valve core 3.

[0036] like Figure 1 , Figure 2As shown, in the valve trim provided in this embodiment, the guide portion 6 and the extension portion 9 have an arc-shaped outer wall. The arc-shaped outer wall enables the guide portion 6 and the extension portion 9 to fit with the inner side wall of the opening of the valve seat 11, thereby enhancing the stability of the guide portion 6 and the limit portion sliding in the valve seat 11. In addition, as an alternative embodiment, the outer walls of the guide portion 6 and the extension portion 9 can also be set as a plane, and the two sides of the outer wall of the plane are slidably matched with the inner side wall of the opening of the valve seat 11.

[0037] like Figure 1 , Figure 2 As shown, the two side edges of the guide portion 6 are arc-shaped, so that a guide port 7 is formed between the two guide portions 6. When the valve core 3 opens the fluid channel, the fluid medium flows in the valve body 10 through the guide port 7 between the two guide portions 6. The two side edges of the arc on the guide portion 6 can guide the fluid medium when it flows through the guide port 7, thereby reducing disturbance. Specifically, the inner side wall of the guide portion 6 is set as a streamlined curved surface structure 8. In addition, as an alternative embodiment, the two side edges of the two guide portions 6 can also be set as straight lines.

[0038] like Figure 2 As shown, in the valve trim provided in this embodiment, the width of the guide port 7 gradually increases in the direction away from the valve core 3. In the process of the valve core 3 opening and closing the fluid channel, the guide portion 6 slides along the valve seat 11. As the distance between the valve core 3 and the valve seat 11 changes, the area of ​​the guide port 7 exposed to the valve seat 11 changes linearly, so that the flow area between the valve core 3 and the valve seat 11 changes, thereby adjusting the flow rate. In addition, as an alternative embodiment, the width of the guide port 7 can also be set to be constant.

[0039] like Figure 2 As shown, in the valve trim provided in this embodiment, there is a gap between the roots of two adjacent guide portions 6. The guide port 7 with a certain flow area between the roots of two adjacent guide portions 6 can prevent the flow area between the valve core 3 and the valve seat 11 from being too small when the valve core 3 is opened slightly. In addition, as an alternative embodiment, the gap between the roots of the two guide portions 6 can be omitted, that is, the roots of the two guide portions 6 are connected as one.

[0040] like Figure 1 As shown, in the valve trim provided in this embodiment, the two sides of the extension portion 9 are straight. The straight sides can make the force on the extension portion 9 uniform. In addition, as an alternative embodiment, the two sides of the extension portion 9 can also be set to be curved or oblique.

[0041] like Figure 1 As shown, in the valve trim provided in this embodiment, a sliding seal is provided between the sealing ring 1 and the valve stem 2. It can prevent the fluid medium in the inner cavity of the welded bellows 4 from leaking outward. Specifically, the sliding seal can adopt a packing seal structure. In addition, as an alternative embodiment, the sealing ring 1 is in sealing contact with the valve cover 12, and a dynamic seal is provided between the valve stem 2 and the valve cover 12.

[0042] like Figure 3 As shown, in the valve trim provided in this embodiment, a sealing member 17 for sealing is detachably provided in the balancing hole 5. The sealing member 17 seals the balancing hole 5, which can convert the balanced valve trim into an unbalanced valve trim. The welded bellows 4 can prevent external leakage, so that the same structure becomes a zero-leakage unbalanced valve with a built-in welded bellows, achieving zero leakage, and greatly increasing the applicable scope of valve trims and valve types. Specifically, the sealing member 17 can be a pin or a stud of the same material as the valve core 3, or it can be welded and sealed, and welded in the balancing hole 5 through a welding block. In addition, as an alternative embodiment, the sealing member 17 can be omitted, and the fluid medium enters the inner cavity of the welded bellows 4 through the balancing hole 5 on the valve core 3, and the unbalanced force is relatively offset, forming a dynamic balance in the valve body 10 to ensure the smooth operation of the valve. The welded bellows 4 can also play a sealing role to prevent internal leakage.

[0043] It should be noted that the valve core 3 may not have the balancing hole 5, and the result is the same as the above 17 and is simpler. When the sealing member 17 blocks the balancing hole 5, the sliding seal between the valve stem 2 and the sealing ring 1 forms a double seal, which strengthens the sealing effect of preventing leakage; or, when the sealing member 17 blocks the balancing hole 5, the sliding seal between the valve stem 2 and the sealing ring 1 may not be set.

[0044] Directions:

[0045] like Figure 1As shown, when the valve trim provided in this embodiment is used, the valve trim is applied to the valve body 10, and the fluid medium enters the inner cavity formed by the welded bellows 4 and the sealing ring 1 through the balance hole 5 on the valve core 3, which can ensure that the valve is dynamically balanced, and the unbalanced forces are relatively offset to ensure the smooth operation of the valve. In the process of the valve core 3 opening the fluid channel, the driving mechanism 16 drives the valve stem 2 to rotate, driving the valve core 3 to move in the direction away from the valve seat 11, the welded bellows 4 is compressed, and the guide portion 6 is slid out of the valve seat 11. The opening position of the valve core 3 is different, and the flow area at the guide port 7 is different to achieve flow regulation. When the valve core 3 is opened to the maximum position, the extension portion 9 cooperates with the inner wall of the opening of the valve seat 11 to reduce the shaking of the valve core 3 and the valve stem 2. In the process of the valve core 3 closing the fluid channel, the driving mechanism 16 drives the valve stem 2 to rotate, driving the valve core 3 to move toward the direction close to the valve seat 11, the welded bellows 4 returns to its original state, the guide portion 6 slides and inserts into the valve seat 11, and the guide port 7 gradually shrinks until it is completely closed.

[0046] In addition, if Figure 1 As shown, this embodiment also provides a straight-stroke valve, comprising: a valve body 10, a valve seat 11, a valve cover 12 and a valve trim described in any one of the above schemes, wherein the valve body 10 has a fluid channel, the valve seat 11 is arranged in the fluid channel, the valve trim is arranged in the valve body 10, the valve trim is in sealing contact with the valve seat 11, and the valve cover 12 is arranged on the upper end surface of the valve body 10. A balanced straight-stroke valve is realized, and the valve body 10 is designed with a built-in welded bellows 4, so that it is small in size and greatly reduces leakage points, and greatly reduces costs without reducing its safety and reliability. Due to the use of the valve trim described in the above embodiment, any of the above advantages is obtained.

[0047] like Figure 1 As shown, in the linear stroke valve provided in this embodiment, a flange is provided in the circumference of the valve core 3, a first groove 13 is provided on the valve seat 11, a static seal is provided in the first groove 13, and the flange is embedded in the first groove 13 in the closed state. When the valve core 3 is closed, the flange is embedded in the first groove 13 and the static seal is squeezed, so as to ensure the sealing between the valve core 3 and the valve seat 11. In addition, as an alternative embodiment, a sealing groove is provided on the valve core 3, and a flange for embedding the sealing groove is provided on the valve seat 11.

[0048] like Figure 1As shown, in the straight-stroke valve provided in this embodiment, a second groove 14 is provided on the valve body 10, and the sealing ring 1 of the valve trim is embedded in the second groove 14. The second groove 14 is provided with a static seal, and the static seal is located between the sealing ring 1 of the valve trim and the valve body 10. During the operation of the valve, the valve cover 12 will generate a dynamic pressing force, and the sealing ring 1 can disperse and evenly transmit the pressure to ensure that the entire circumferential surface is evenly stressed, thereby protecting the static seal in the second groove 14 from unnecessary damage, keeping the static seal from deforming after being stressed, and avoiding leakage. Specifically, a sealing ring can be used for the static seal. In addition, as an alternative embodiment, the second groove 14 can be provided on the sealing ring 1, and the upper end surface of the valve body 10 is provided with an annular protrusion for embedding the second groove 14.

[0049] like Figure 1 As shown, in the straight-stroke valve provided in this embodiment, a sealing cavity 15 is provided at the top of the valve cover 12, and the portion of the valve stem 2 extending out of the valve cover 12 is located in the sealing cavity 15. A driving mechanism 16 is provided above the sealing cavity 15, and the driving rod of the driving mechanism 16 extends into the sealing cavity 15 and is connected to the valve stem 2. The sealing cavity 15 can protect the valve stem 2 extending out of the valve cover 12, and the valve stem 2 is driven to rotate by the driving mechanism 16, thereby driving the valve to operate. Specifically, the driving mechanism 16 is configured as a motor. In addition, as an alternative embodiment, the driving mechanism 16 can be omitted, and a handwheel is provided at the end of the valve stem 2. The user manually rotates the handwheel to drive the valve stem 2 to rotate, thereby realizing the operation of the valve.

[0050] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the present invention.

Claims

1. A valve trim, for being arranged in a valve body (10), characterized in that: include: A sealing ring (1), wherein a valve stem (2) is inserted into the sealing ring (1); A valve core (3) is arranged at the end of the valve stem (2), the valve core (3) is used to close the opening and closing of the fluid channel in the valve body (10), the valve core (3) has an extension portion (9) extending toward the fluid channel, and during the process of the valve core (3) opening and closing the fluid channel, the extension portion (9) always slides with the inner wall of the fluid channel; A welding bellows (4) is sleeved on the outer side of the valve stem (2), the first end of the welding bellows (4) is welded to the sealing ring (1), the second end of the welding bellows (4) is welded to the valve core (3), and a balancing hole (5) is provided on the valve core (3), and the balancing hole (5) passes through the valve core (3) so that the inner cavity of the welding bellows (4) is connected to the fluid channel.

2. The valve trim according to claim 1, characterized in that: The valve core (3) has a guide portion (6) extending toward the fluid channel, the guide portion (6) has a plurality of guide portions (6) arranged at circumferential intervals around the valve core (3), and the extension portion (9) is arranged at the extension end of the guide portion (6).

3. The valve trim according to claim 2, characterized in that: The guide portion (6) and the extension portion (9) both have arc-shaped outer walls.

4. The valve trim according to claim 2, characterized in that: Both side edges of the guide portion (6) are arc-shaped, so that a guide port (7) is formed between the two guide portions (6).

5. The valve trim according to claim 4, characterized in that: The width of the guide port (7) gradually increases in a direction away from the valve core (3); And / or, there is a gap between the roots of two adjacent guide parts (6).

6. The valve trim according to any one of claims 2 to 5, characterized in that: Both side edges of the extension portion (9) are straight lines.

7. The valve trim according to any one of claims 1 to 5, characterized in that: A sliding seal is provided between the sealing ring (1) and the valve stem (2).

8. The valve trim according to any one of claims 1 to 5, characterized in that: A sealing member (17) for sealing is detachably arranged in the balancing hole (5).

9. A linear valve, characterized in that: include: A valve body (10), a valve seat (11), a valve cover (12) and a valve trim as described in any one of claims 1 to 8, wherein the valve body (10) has a fluid channel, the valve seat (11) is arranged in the fluid channel, the valve trim is arranged in the valve body (10), the valve trim is in sealing contact with the valve seat (11), and the valve cover (12) is arranged on the upper end surface of the valve body (10).

10. The linear stroke valve according to claim 9, characterized in that: The valve core (3) is provided with a flange in the circumference thereof, the valve seat (11) is provided with a first groove (13), a static seal is provided in the first groove (13), and in a closed state, the flange is embedded in the first groove (13); The valve body (10) is provided with a second groove (14), the sealing ring (1) of the valve trim is embedded in the second groove (14), the second groove (14) is provided with a static seal, and the static seal is located between the sealing ring (1) of the valve trim and the valve body (10); A sealing cavity (15) is arranged on the top of the valve cover (12), and the portion of the valve stem (2) extending out of the valve cover (12) is located in the sealing cavity (15). A driving mechanism (16) is arranged above the sealing cavity (15), and a driving rod of the driving mechanism (16) extends into the sealing cavity (15) and is connected to the valve stem (2).

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